During the first continuation year of this project, it is proposed to correlate the biochemical findings which already have been made with morphological observations involving transmission electron microscopy, combined with appropriate fluorescence and isotope studies, on the general subject of glycogen metabolism in human skin fibroblasts grown in tissue culture. The aim of the study is to gather information on the autophagy of glycogen in such cells, to measure quantitatively the rate of this process, and to compare it with the rate of glycogen hydrolysis within lysosomes. Normal control cells and cells from patients with various types of glycogen storage disease will be used. It is hoped that these studies will shed light on phenotypic differences in the glycogen metabolism of cells which have the same genetic defect (lack of lysosomal alpha-glucosidase, Type II glycogen storage disease).